Many currently available computing devices run operating systems that offer users the opportunity to run several software applications at the same time, and even to perform several activities simultaneously, within a single software application and/or among two or more software applications. For example, a user may open an e-mail application, a word processing application, an on-screen calculator, and a web browser, so that all of the applications are open concurrently. The user may open several documents within the word processing application, and may open several e-mail messages. Such an arrangement allows the user to move from one task to another by keeping these various applications and activities open at the same time.
Various visual paradigms are available for presenting multiple concurrently running applications and other activities within a graphical user interface. In some computing systems, multiple overlapping windows are made available, with each window representing an application, document, task, or other activity. A desktop metaphor is often employed, wherein the user can move and resize windows on a display screen by direct manipulation. At any given time, one window has focus (usually indicated as such by being situated on top of the other windows). Other windows may be visible, invisible, or partially visible (for example if they are partially or completely obscured by other windows). A user can switch from one activity to another by causing a different window to have focus; this is commonly accomplished by clicking on a visible portion of the window being activated, or by clicking on a button or icon representing the window in a task bar, quick-launch area, or similar construct. In some operating systems, pop-up menus and/or keyboard shortcuts may be available for switching among applications, documents, or other activities.
In other systems, a card metaphor is used, in which each application or other activity can be represented within an area of the screen. Cards can be moved on a display screen, for example by direct manipulation via a touch-screen user interface. Several card viewing modes can be provided. Various embodiments of a card metaphor are described in related U.S. patent application Ser. No. 12/126,145, filed May 23, 2008, for “Navigating Among Activities in a Computing Device”, and related U.S. patent application Ser. No. 12/416,279, filed Apr. 1, 2009, for “Card Metaphor for Activities in a Computing Device”, the disclosures of which are incorporated herein by reference.
Such systems provide mechanisms by which several applications and/or other activities can be kept open concurrently, allowing a user to easily switch between activities with minimal overhead. The ability to keep several activities open is advantageous because it avoids the need to repeatedly open and close applications. In addition, many systems (including those described above) allow users to view output from (and/or interact with) two or more activities on a common screen (or on multiple screens) at the same time. Cards or windows from two or more applications can be displayed simultaneously, allowing a user to refer to one while interacting with another, or to perform other tasks that involve interaction with two or more applications. Certain operations benefit greatly from such an arrangement, such as, for example, cutting and pasting content from one application to another.
Mobile devices such as smartphones, personal digital assistants, music players, handheld computers, and the like are becoming increasingly powerful. Many are now able to run several applications concurrently, and to perform sophisticated functions that rival traditional computing devices. However, many such devices have limited computing resources, including limited processor speed and/or available memory. Owing to these limitations, such devices can often run a limited number of applications concurrently; exceeding the limit can cause poor performance, instability, crashes, or other detrimental effects.
In such devices, if a user attempts to open an application, open a document, or initiate another activity that causes a memory or processing limit to be reached, the user may be presented with an error message informing him or her that the requested task cannot be performed unless some applications, documents, windows, cards, or other activities are closed first. Alternatively, the user may be presented with a message simply informing him or her that there is no memory left. At worst, the system may crash and the user may lose valuable data that he or she was working on.
None of these scenarios are satisfactory. What is needed is a system and method that handles resource limitations without impinging on the user's ability to perform the task he or she wishes to perform. What is further needed is a system and method that allows a user to open an activity even when many other activities have been opened, and even in the face of resource limitations on the computing system.
Even when a resource limit is not reached, the continued operation of an activity can be wasteful in terms of system resources, thus having a deleterious effect on the performance of the computing device. Running an application, or keeping a document open, that is not needed can consume valuable computing resources, including memory, processing time, network bandwidth, battery power, or any combination thereof. In some situations, users leave applications and/or documents open even when they are not needed. The user may not realize that an activity still running, or may not understand that the activity is consuming a significant amount of system resources. What is needed, therefore, is a system and method for detecting such conditions and avoiding wasteful use of system resources for activities that are left open but are not in active use.